Vinylidene fluoride copolymers comprising recurring units derived from (meth)acrylic monomers are known in the art for being endowed with suitable hydrophilic properties and enhanced adhesion towards metals other than chemical inertness and mechanical properties typical of the vinylidene fluoride homopolymers.
Due also to their well-known electrochemical stability, high crystallinity and melting point, chemical resistance in electrolytes and solubility in few selected solvents, vinylidene fluoride copolymers comprising recurring units derived from (meth)acrylic monomers have been thus found to be suitable for the manufacture of electrodes and membranes which are typically shaped by processing solutions of said copolymers in suitable organic solvents.
In particular, EP 1621573 A (KUREHA CORPORATION) 1 Feb. 2006 discloses porous membranes of vinylidene fluoride copolymers comprising from 0.01% to 10% by moles of hydrophilic monomer units having at least one group selected from epoxy, hydroxyl, carboxy, ester, amide and acid anhydride groups, said membranes being obtained by melt-extruding compositions of said copolymers comprising well-defined amounts of suitable organic solvents and plasticizers.
Vinylidene fluoride copolymers comprising recurring units derived from (meth)acrylic monomers are also known in the art which, due to random distribution of (meth)acrylic monomers within the polyvinylidene fluoride backbone of the fluorocopolymer, advantageously maximize the effects of the modifying (meth)acrylic monomer on both the adhesiveness and/or the hydrophylic behaviour of the resulting copolymer, even at low levels of (meth)acrylic monomer in the composition, without impairing the other outstanding properties of the vinylidene fluoride polymers, e.g. thermal stability and mechanical properties.
For instance, WO 2008/129041 (SOLVAY SOLEXIS S.P.A.) 30 Oct. 2008 discloses linear semi-crystalline copolymers of vinylidene fluoride comprising from 0.05% to 10% by moles of recurring units derived from (meth)acrylic monomers, said copolymers having a random distribution of the recurring units derived from hydrophilic (meth)acrylic monomers throughout the whole vinylidene fluoride backbone, and use thereof as binders, especially for forming electrodes of Lithium batteries and/or electric double layer capacitors, or for the manufacture of hydrophilic membranes.
However, among major issues affecting solution processing of the vinylidene fluoride copolymers of the prior art, mention can be notably made of poor dissolution properties of said copolymers in common organic solvents, so that long dissolution times are typically required at low temperatures for obtaining uniform and stable solutions of these copolymers at concentrations suitable for preparing electrodes and membranes.
It would thus be desirable to find alternative vinylidene fluoride copolymers which advantageously offer increased dissolution properties in suitable organic solvents, while maintaining good thermal stability properties.